1. Field of the Invention
The present invention concerns an antenna arrangement for acquisition of a magnetic resonance signal with at least two acquisition antennas, of the type wherein each of the acquisition antennas has at least one conductor loop and the conductor loops each exhibit an interruption (gap), and wherein the conductor loops are connected in parallel at the interruptions and a capacitive decoupling element is connected at least at one of the interruptions, the capacitive coupling element exhibiting a capacitance at which both acquisition antennas are decoupled from one another.
2. Description of the Prior Art
In antenna arrangements with a number of individual antennas, a radio-frequency current in one antenna can induce a voltage in an adjacent individual antenna, known as coupling. The coupling can be present both in circularly polarized antenna arrangements, wherein two antenna systems are aligned perpendicular to one another, and in antenna arrays wherein the individual antennas generally possess the same alignment. Couplings generally worsen the signal-to-noise ratio (S/N ratio) of the overall signal. In addition, the effort for compensation and testing of coupled individual antennas is greater than for compensation and testing of uncoupled individual antennas. It is therefore desirable to prevent coupling of individual antennas.
An antenna arrangement for a magnetic resonance apparatus of the initially-described general type is known from DE 195 36 531 C2. Two adjacent individual antennas each exhibit an interruption (gap). Each interruption is bridged with a capacitive element, so the individual antennas are decoupled. Possible couplings of the individual antennas via a common mode current created on the connection lines are suppressed by a sheath wave barrier.
Damping of the differential signal necessary for decoupling of the individual antennas and by the capacitive element, however, results due to the sheath wave barrier.
An RF coil for magnetic resonance imaging is described in U.S. Pat. No. 6,348,794, in which three acquisition antennas are electronically connected in parallel via two lines. Each of the acquisition antennas is formed by a conductor loop that exhibits an interruption. A capacitive element is arranged in each interruption. A further capacitive element is arranged in the parallel connections between the conductor loops. In one embodiment, an inductor, which can be connected or disconnected via a diode arrangement, is connected in parallel with the capacitive element in one of the connections between the conductor loops.